CHEMICAL PRINCIPLES. 
367 
nearly about ten for an hundred of oxigen gas, which agrees Metallic o*-< 
tolerably well with the calculation. Fourcroy maintains that ’ 
this super-oxide should contain forty for a hundred of oxigen. 
Adopting the analysis which I made for discovering the cotn- 
posirion of the manganic oxide, as the most correct, as it 
also is the most simple, it follows that the oxides of 
manganese are composed according to the following state- 
ment ; 
metal, oxigen. metal, oxigen. 
SuboxiJum mang.inicum. . . . B/,08. . 12,32.. . . 100 .. . 14,0533 
Oxidum manganosum 78 , 10 . . 21 , 90 . . .. — ...28,10/7 
Oxidum manganicum 7l^»25. .2Q.75.. . . — . . .42,l600 
Superoxidum manganicum.. . 64,00. . 36,00. ... — . . .50,215 
JX. Experiments on the suboxides of some Metals. 
(a) Snboxidum bismiithicum. 
It is well known that bismuth when melted by a moderate 
heat, becomes covered with a purple powder. The same thing 
happens if powdered bismuth is exposed for a length of time 
to the action of the air. I had exposed bismuth in powder to 
the influence of atmospheric air in an o|)en phial during the 
summer months. The upper part of the metal I found con- 
verted into a powder of a deep purple colour. This part was 
more divided than the lower part, to which the action of the 
air had not penetrated. I here was a very marked limit be- 
tween the metallic part and the part suboxided. I took away 
some of this latter, wdiich I treated with the concentrated 
muriatic acid. 7'he subtixide was decomposed, and the result 
consisted of muviat of bismuth, and bismuth reduced. 
I must here remind the reader, that it is one of the cha- 
racters of this class of oxided bodies, not to combine with 
other oxides, without undergoing a similar decomposition. 
{!') Suloxidum plumlicum. 
We know that lead when exposed to the atmosphere, be- 
comes covered by degrees with a pellicle of a deeper colour 
Appendix. VoL. XXXVI. — No. 170 . Ee than 
